Systems for controlling exhaust emissions produced by an internal combustion engine are known and have been widely implemented, particularly in the heavy-duty diesel engine industry. Historically, the Environmental Protection Agency (EPA) has promulgated limits for allowable levels of certain exhaust emissions such oxides of nitrogen (NOx). However, such emission level requirements promulgated by the EPA are typically subject to frequent changes that are often difficult to integrate into existing engine control logic.
The EPA has recently provided for the possibility of allowing engine behavior that deviates from “normal” or expected engine operation while meeting emission requirements through the use of one or more auxiliary emission control devices or AECDs, wherein an AECD is defined for purposes of the subject invention as a software structure that defines, as a function of one or more engine operating parameters, a current operational state of the engine. As an example, a particular AECD may define an engine speed AECD responsive to at least a signal produced by an engine speed sensor to produce one or more control outputs. It is to be understood that this example is provided only by way of illustration and is not necessarily indicative of a practical AECD. In any case, the use of any one or more AECDs with a particular engine configuration is, at present, privately negotiated with the EPA by the individual engine manufacturer, and the number as well as the functions of the one or more permitted AECDs are accordingly considered by the various engine manufacturers to be highly confidential. Like emission requirements, AECD definitions permitted by the EPA are also subject to frequent changes, wherein assimilation of newly permitted AECDs as well as abandonment of, or changes to, existing AECDs are likewise difficult to implement into known engine control routines.
One drawback associated with known systems for implementing EPA-mandated emission requirements as well as negotiated AECD definitions is that there typically exists an interdependency between the emissions/AECD logic and the base engine control routines. What is therefore needed is a system that isolates emission requirements/allowances from base engine control logic. Such a system should be easily adaptable to changing emission requirements and/or AECD definitions and sufficiently flexible to accommodate any number of AECDs.